The present invention relates to a hydraulic system for a hydraulic cylinder, in particular of the differential piston type. The invention provides for a pump to deliver fluid from a reservoir into the cylinder space which volume increases when the piston moves, wherein fluid displaced from the opposite cylinder space is pressurized from applying a hydraulic bias force to the piston.
The term hydraulic biasing the piston of a hydraulic cylinder means that the piston is displaced against a hydraulic pressure which is generated in the cylinder space from which the fluid is displaced by the moving piston. It is known for this type of hydraulic circuits that the fluid delivered by a pump is supplied to one of the cylinder spaces through a directional control valve and the fluid displaced from the other cylinder space is returned via a directional valve and a throttling means to the reservoir. By adjusting the throttle the desired counter pressure or biasing pressure is selected.
The object of the present invention is to generate the counter pressure in a novel manner involving various advantages and to provide a hydraulic system to precisely control the counter pressure substantially free of hydraulic losses.